Wheel lock control differential

ABSTRACT

A differential unit has ring gears formed on the inner diameters of the side gears, which are connected to inboard discs for vehicle braking. Planetary gears in the ring gears are rotatably mounted on carriers which transmit power to the axle shafts. The planetary gears also mesh with sun gears which are fastened to a modulator pump shaft. The modulator pump housing is a part of the differential pinion gear axle. The pump includes an integral bypass valve which is normally closed so as to hydraulically lock the pump. The valve is controlled through a wheel sensor and a logic box which may be of the type of wheel lock control currently in production on several automotive vehicles. During normal operation, the differential acts in the same manner as the usual differential. During braking, the brake torque is carried by the pump. When an incipient wheel lock condition is approached, the pump by-pass valve is opened. The pump is no longer hydraulically locked and therefore allows the sun gears to rotate. This also permits the planetary gears, the carrier axle shafts and the wheels connected thereto to rotate. When the valve is again closed, the system returns to the normal driving condition.

United States Patent Weisgerber 51 Sept. 12,1972

[ WHEEL LOCK CONTROL DIFFERENTIAL [72] Inventor: Thomas W. Weisgerber,Saginaw,

Mich.

[73] Assignee: General Motors Corporation, Detroit, Mich.

[221 Filed: Aug. 27, 1971 [21] Appl.No.:173,504

Primary Examiner-Benjamin W. Wyche Attorney-W. E. Finken [5 7] ABSTRACTA differential unit has ring gears formed on the inner diameters of theside gears, which are connected to inboard discs for vehicle braking.Planetary gears in the ring gears are rotatably mounted on carrierswhich transmit power to the axle shafts. The planetary gears also meshwith sun gears which are fastened to a modulator pump shaft. Themodulator pump housing is a part of the differential pinion gear axle.The pump includes an integral by-pass valve which is normally closed soas to hydraulically lock the pump. The valve is controlled through awheel sensor and a logic box which may be of the type of wheel lockcontrol currently in production on several automotive vehicles. Duringnormal operation, the differential acts in the same manner as the usualdifferential. During braking, the brake torque is carried by the pump.When an incipient wheel lock condition is approached, the pump by-passvalve is opened. The pump is no longer hydraulically locked andtherefore allows the sun gears to rotate. This also permits theplanetary gears, the carrier axle shafts and the wheels connectedthereto to rotate. When the valve is again closed, the system returns tothe normal driving condition.

9 Claims, 1 Drawing Figure PAIENTEUSEP 12 me 3.690.426

I NVEN TOR.

.74022205 1/ Z/yezez B Y A T TOQ/VEY WE]. LOQK CONTROL DIFFERENTIAL Theinvention relates to a modulated differential type of wheel lock controlutilizing a modification of the usual automotive differential. One ofthe advantages of the system is that it is automatically operable. It isalso integral with the differential and the oil used is the same oilused for differential gear lubrication. It is also an advantage that theentire brake system remains integral and has no hydraulic connectionwith the wheel lock control.

Under normal driving operations, the unit acts as the usualdifferential. However, when the brakes are applied so as to cause thewheels connected to the differential to lose speed or deceleratesufficiently to create incipient wheel lock, the system becomesoperative. When the wheels accelerate and again reach a condition wherewheel lock is no longer incipient, the system is returned to the normaldifferential operating condition. It may cycle during a braking stop, ifnecessary, in order to control wheel lock.

IN THE DRAWING:

I The single FIGURE is a cross-section view, with parts broken away andsome parts illustrated schematically, showing a vehicle differential andbrake system with the invention embodied in the differential.

The vehicle in which the system is installed has a braking system whichis schematically illustrated as including a pedal 12 actuating a mastercylinder 14 to deliver brake actuating pressure to one pair of wheelsthrough conduit 16 and to another pair of wheels through conduit 18. Inthe preferred embodiment, conduit 18 is connected to the rear wheelbrake calipers 20 and 22.

The differential assembly 24 includes a drive shaft 26 connected to bedriven by the vehicle engine in a well known manner, and output shaftsor axles 28 and 30.

These shafts extend in opposite directions and are respectivelyconnected through universal joints 32 and 34 to the vehicle drivewheels, one such wheel 36 being illustrated.

The wheel lock control system includes a wheel condition sensor 38 whichgenerates signals indicating the rotational condition of the wheel. Whenwheel lock is incipient, the sensor 38 generates and delivers anappropriate signal to the logic box 40 which in turn controls a portionof the system to be described. The sensor 38 and the logic box 40 may beof any suitable type such as that currently manufactured as parts ofwheel lock control systems available on several automotive vehicles. Theoutput signal from the logic box is an onoff type signal in its simplestform, although it can be readily seen that under some conditions thesystem could be refined to have intermediate signals and con trols.

The differential assembly 24 includes a housing 42 into which the driveshaft 26 projects. A drive pinion 44 is rotatably driven by the driveshaft and is located in the housing differential chamber 46. The drivepinion 44 engages the ring gear 48, which is mounted on the pinion axleso that the ring gear rotates the pinion axle about the axis of thedifferential opposed output axles 28 and 30. Pinion axle 50 carries twodrive the two side gears gears 52 and 54 which in turn drive 56 and 58.When the vehicle is driven in a straight line there is no relativemotion between the two side gears and the two pinion gears do not rotateon their axle. If there is relative motion between the two side gears,such as in a turn, the pinion gears 52 and 54 rotate on the pinion axle50 and sustain the transmission of power through the gears whileallowing the required differential action. Up to this point, thedifferential is similar in form and function to the standardproduction-type differential.

The side gears 56 and 58 respectively have ring gears 60 and 62 formedor otherwise provided on their inner diameters. These ring gears areparts of a planetary gear train. The side gears have quill shaftsections 64 and 66 extending outwardly of the housing 42 and about axles28 and 30 and provided with inboard braking discs 68 and 70. The brakecalipers 20 and 22 are positioned to provide friction braking byengagement of brake pads on the braking surfaces of the disc 68 and 70when the master cylinder 14 is actuated. Other types of brakingarrangements can be utilized without departing from the invention.

The inner ends of axles 28 and 30 are respectively connected toplanetary gear carriers 72 and 74 and the planetary gear sets 76 and 78are respectively mounted on these carriers. Planetary gear set 76 mesheswith ring gear 60 and planetary gear set 78 meshes with ring gear 62.The planetary gear train also includes sun gears 80 and 82 whichrespectively mesh with planetary gear sets 76 and 78 and are attached toa through shaft 84.

The pinion axle 50 has a central section forming a modulator pumphousing 86 which is a part of the modulator pump assembly 88. The pumpincludes a positive displacement pump member 90 attached to shaft 84 andlocated in a sealed pump chamber. The pump housing 86 is suitably portedand formed to provide a by-pass passage 92 connecting the input andoutput portions of the sealed pump chamber. A control valve 94 ispositioned in the passage 92 to control the flow of hydraulic fluidbetween the pump inlet and the pump outlet. When valve 94 is closed, asit normally is, the pump is hydraulically locked so that the housing 86and the pump member 90 rotate about the axis of shaft 84 when ring gear48 is rotated. The pump is at pressure at all times that power is beingdelivered by the planetary gear train, and in proportion to the amountof power transmitted. However, no power is absorbed and no heat isgenerated because there is no pump fluid flow. Under this condition ofdriving operation, the ring gear 48, the pinion axle 50, the piniongears 54, the side gears 56 and 58 with their shafts 64 and 66 and discs68 and 70, the pump housing 86, the pump member 90, the through shaft84, and the sun gears 80 and 82, rotate in unison. Therefore, theplanetary gear sets 76 and 78 also rotate in unison with them as do theaxles 28 and 30 and, therefore, the vehicle wheels are driven.

Under normal driving conditions, there is no need for the wheel lockcontrol system to function and driving power from the vehicle engine istransmitted through the difierential assembly 24 in the normal manner.When sufficient brake line pressure is applied by the master cylinder 14to the brake calipers 20 and 22 to cause the discs 68 and 70 to beretarded, braking action is efiected on the wheel 36 and the similarwheel on the other side. The braking action is effected through theaxle-planet carrier-planet gear set-sun gear system.

Brake torque is carried by the pump 88 just as driving torque is carriedand in the same rotational direction.

When sufficient brake line pressure is applied to cause the associatedvehicle wheels to reduce speed or decelerate in such a manner as toreach incipient wheel lock, the sensor 38 generates and sends anappropriate signal to the logic box 40 indicating this condition. Thelogic box in turn generates a signal which is sent to the control valve94. The sensor and logic box functions are well known in the art and anysuitable construction and arrangement known in the art may be used. Thesignal received by the control valve 94 causes that valve to open andallow pump fluid flow through the valve from the pump outlet to the pumpinlet through by-pass passage 92. This allows the pump output shaft 84to rotate and, therefore, allows the sun gears 80 and 82 to rotaterelative to the pinion axle 50 and the side gears 56 and 58. This allowsrotation of the planetary gear sets 76 and 78 and thus rotation of theplanetary carriers 72 and 74. Therefore, the axles 28 and 30 and thewheels connected thereto are permitted to rotate at a faster speed thanbefore, thereby moving away from an incipient wheel lock condition. Thesensor 38 then signals the logic box 40 that wheel lock is no longerincipient and the logic box sends a different signal to control valve94, causing the valve to close. This again hydraulically locks the pumpand the rear wheels again slow down if the brakes are still applied.This cycle is repeated during a braking stop so as to generate acontrolled stop without wheel locking even though the brakes may besufficiently applied to otherwise cause one or more wheels to be locked.The system is not required to operate directly or indirectly on thehydraulic braking circuits or other portions of the braking system,thereby maintaining braking circuit integrity and independence. Thesystem may also be applied to other than driving wheels by theappropriate use of differentially connected wheels.

What is claimed is:

l. A vehicle wheel lock control differential comprisa differential inputmember;

first and second differential intermediate members;

first and second differential output membersrespectively associated withsaid first and second differential intermediate members and eachoperatively connected to a vehicle wheel;

means normally locking said members for concurrent rotation;

means selectively braking at least one of Said intermediate members;means operatively sensing incipient lock of at least one of said wheelsin response to actuation of said selectively braking means and externalconditions affecting said output members and generating an incipientlock signal; and means receiving said incipient lock signal andcontrolling said locking means to unlock same and permit said outputmembers and said wheels to rotate at speeds'greater than the speed ofrotation of said braked intermediate member.

2. The vehicle wheel lock control differential of claim I in which eachof said intermediate members includes a differential side gear and aplanetary gear set composed of a sun gear and a ring gear on said sidegear and a planetary carrier drivingly connected with one of said outputmembers and planetary gears on said carrier and meshing with said ringgear and said sun gear.

3. The vehicle wheel lock control differential of claim 1 in which saidinput member includes a differential ring gear and a pinion axle drivenby said ring gear and pinion gears rotatably mounted on said pinionaxle, each of said intermediate members includes a planetary gear sethaving a ring gear driven by said input member and a sun gear and aplanetary carrier connected to one of said output members and planetarygears mounted thereon and meshing with said planetary ring gear,

said sun gear and said pinion axle having said locking means associatedtherewith and operatively locking them together for concurrent andunitary rotation when the locking means is locked and unlocking them forindependent rotation when the locking means is unlocked.

4. The vehicle wheel lock control differential of claim 1, each of saidintermediate members comprising a differential side gear driven by saidinput member,

a planetary gear set composed of an internal ring gear on saiddifferential side gear and a sun gear and a carrier drivingly connectedto one of said output members and planetary gears rotatably mounted onsaid carrier and meshing with said internal ring gear and saidsun gear,

said braking means including a disc on each of said differential sidegears and a brake caliper assembly for braking each disc.

5. In a differential having pinion drive gears mounted on a pinion axle,planetary carrier output members connected to vehicle wheels, first andsecond side ring gears driven by said pinion drive gears, planetarygears driven by said side ring gears and mounted on said carrier outputmembers, and sun gears meshing with said Pl y gears;

a positive displacement pump assembly having a housing forming a part ofsaid pinion axle and movable therewith as a pump drive member, an outputshaft secured to said sun gears for rotation therewith and providing apump driven member;

a pump bypass passage in said housing with selectively opened and closedcontrol valve means therein operating to hydraulically lock said pumpdrive member and driven member for unitary rotation when said valvemeans is closed and to unlock same to permit rotation of said pumpdriven member relative to said pump drive member when said valve meansis open;

and vehicle wheel lock sensing and control means selectively operatingsaid control valve means to prevent wheel lock during braking.

6. A vehicle brake and wheel lock control system comprising:

a differential including opposed side gears, pinion gears mounted on thepinion axle of a pinion axle assembly and meshing with said opposed sidegears in driving relation, first and second internal ring gearsrespectively on said opposed side gears;

first and second planetary carriers respectively having first and secondsets of planetary gears rotatably mounted thereon respectively meshingwith said first and second internal ring gears;

and first and second sun gears respectively meshing with said first andsecond sets of planetary gears and rotatably mounted on said pinion axleassembly;

first and second vehicle wheels respectively drivingly connected withsaid first and second planetary carriers;

brake means on said opposed side gears selectively actuable to brake thevehicle;

means drivingly intermediate said pinion axle and said sun gears andforming a part of said pinion axle assembly and selectively locking saidsun gears for rotation with said pinion axle and unlocking said sungears for rotation independently of rotation of said pinion axle;

means sensing a rotational characteristic reflecting wheel slip duringbrake application and generating an incipient wheel lock signal whenexcessive wheel slip occurs;

and means receiving said incipient wheel lock signal and controllingsaid selectively locking and unlocking means to unlock said selectivelylocking and unlocking means when said signal is received and to locksaid selectively locking and unlocking means when said signal is notreceived.

7. The system of claim 6 in which said differential is a powertransmitting differential having means driving said pinion axle totransmit power to said vehicle wheels.

8. The system of claim 6 in which said selectively locking and unlockingmeans is a hydraulic fluid pump.

9. The system of claim 8 in which said hydraulic fluid pump has a driveinput driven by movement of said pinion axle, driven output meansdrivingly connected with said sun gears, a hydraulic fluid returnpassage connecting the pump fluid input and output to return hydraulicfluid from the pump fluid output to the pump fluid input, and valvemeans in said passage selectively closed and opened to respectivelyhydraulically lock and unlock said pump drive input and driven outputmeans, said controlling means controlling the opening and closing ofsaid valve means.

P tent N 3,690,426 Dated September 12, 1972 In fis) Thomas W. WeisqerberIt is certified that" error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

[ Column 1, lines 64, 65 and 66, the sentence "Pinion axle 50 carriestwo drive the two side gears 52 and 54 which in turn drive 56 and 58."should read Pinion axle 50 carries two pinion gears 52 and 54 which inturn drive the two side gears 56 and 58.

Signed arid sealed this 20th day of February 1973 I (SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

1. A vehicle wheel lock control differential comprising: a differentialinput member; first and second differential intermediate members; firstand second differential output members respectively associated with saidfirst and second differential intermediate members and each operativelyconnected to a vehicle wheel; means normally locking said members forconcurrent rotation; means selectively braking at least one of saidintermediate members; means operatively sensing incipient lock of atleast one of said wheels in response to actuation of said selectivelybraking means and external conditions affecting said output members andgenerating an incipient lock signal; and means receiving said incipientlock signal and controlling said locking means to unlock same and permitsaid output members and said wheels to rotate at speeds greater than thespeed of rotation of said braked intermediate member.
 2. The vehiclewheel lock control differential of claim 1 in which each of saidintermediate members includes a differential side gear and a planetarygear set composed of a sun gear and a ring gear on said side gear and aplanetary carrier drivingly connected with one of said output membersand planetary gears on said carrier and meshing with said ring gear andsaid sun gear.
 3. The vehicle wheel lock control differential of claim 1in which said input member includes a differential ring gear and apinion axle driven by said ring gear and pinion gears rotatably mountedon said pinion axle, each of said intermeDiate members includes aplanetary gear set having a ring gear driven by said input member and asun gear and a planetary carrier connected to one of said output membersand planetary gears mounted thereon and meshing with said planetary ringgear, said sun gear and said pinion axle having said locking meansassociated therewith and operatively locking them together forconcurrent and unitary rotation when the locking means is locked andunlocking them for independent rotation when the locking means isunlocked.
 4. The vehicle wheel lock control differential of claim 1,each of said intermediate members comprising a differential side geardriven by said input member, a planetary gear set composed of aninternal ring gear on said differential side gear and a sun gear and acarrier drivingly connected to one of said output members and planetarygears rotatably mounted on said carrier and meshing with said internalring gear and said sun gear, said braking means including a disc on eachof said differential side gears and a brake caliper assembly for brakingeach disc.
 5. In a differential having pinion drive gears mounted on apinion axle, planetary carrier output members connected to vehiclewheels, first and second side ring gears driven by said pinion drivegears, planetary gears driven by said side ring gears and mounted onsaid carrier output members, and sun gears meshing with said planetarygears; a positive displacement pump assembly having a housing forming apart of said pinion axle and movable therewith as a pump drive member,an output shaft secured to said sun gears for rotation therewith andproviding a pump driven member; a pump bypass passage in said housingwith selectively opened and closed control valve means therein operatingto hydraulically lock said pump drive member and driven member forunitary rotation when said valve means is closed and to unlock same topermit rotation of said pump driven member relative to said pump drivemember when said valve means is open; and vehicle wheel lock sensing andcontrol means selectively operating said control valve means to preventwheel lock during braking.
 6. A vehicle brake and wheel lock controlsystem comprising: a differential including opposed side gears, piniongears mounted on the pinion axle of a pinion axle assembly and meshingwith said opposed side gears in driving relation, first and secondinternal ring gears respectively on said opposed side gears; first andsecond planetary carriers respectively having first and second sets ofplanetary gears rotatably mounted thereon respectively meshing with saidfirst and second internal ring gears; and first and second sun gearsrespectively meshing with said first and second sets of planetary gearsand rotatably mounted on said pinion axle assembly; first and secondvehicle wheels respectively drivingly connected with said first andsecond planetary carriers; brake means on said opposed side gearsselectively actuable to brake the vehicle; means drivingly intermediatesaid pinion axle and said sun gears and forming a part of said pinionaxle assembly and selectively locking said sun gears for rotation withsaid pinion axle and unlocking said sun gears for rotation independentlyof rotation of said pinion axle; means sensing a rotationalcharacteristic reflecting wheel slip during brake application andgenerating an incipient wheel lock signal when excessive wheel slipoccurs; and means receiving said incipient wheel lock signal andcontrolling said selectively locking and unlocking means to unlock saidselectively locking and unlocking means when said signal is received andto lock said selectively locking and unlocking means when said signal isnot received.
 7. The system of claim 6 in which said differential is apower transmitting differential having means driving said pinion axle totransmit power to said vehicle wheels.
 8. The system of claim 6 in whichsaid selecTively locking and unlocking means is a hydraulic fluid pump.9. The system of claim 8 in which said hydraulic fluid pump has a driveinput driven by movement of said pinion axle, driven output meansdrivingly connected with said sun gears, a hydraulic fluid returnpassage connecting the pump fluid input and output to return hydraulicfluid from the pump fluid output to the pump fluid input, and valvemeans in said passage selectively closed and opened to respectivelyhydraulically lock and unlock said pump drive input and driven outputmeans, said controlling means controlling the opening and closing ofsaid valve means.